<!doctype html>
<html>
  <head>
    <meta charset=utf-8>
    <title>Reference green box</title>
    <style>
      div {
        width: 100px;
        height: 100px;
        background: green;
      }
    </style>
  </head>
  <body>
    <div></div>
  </body>
</html>
